1. Field of the Invention
Exemplary aspects of the present invention generally relate to an image forming apparatus, and more particularly, to an image forming apparatus including a recording head mounted on a carriage that reciprocally travels back and forth.
2. Description of the Background Art
There is known an image forming apparatus, such as a printer, a facsimile machine, a copier, and a multi-functional system having a plurality of these functions thereof, which employs an ink jet recording device for ejecting ink onto a recording medium such as a sheet of paper to form an image thereon.
Such an ink jet recording device uses, for example, a recording head that ejects liquid droplets of ink.
In the image forming apparatus of this type, an image forming operation is conducted by the recording head that ejects ink droplets onto a recording medium, typically although not necessarily a sheet of paper. It is to be noted that the image forming operation mentioned herein refers to any operation by which an image is fixed in tangible form, whether by recording, printing, imaging, or some other process or combination of processes.
Such an image forming apparatus is generally classified into two types, a serial-type image forming apparatus and a line-type image forming apparatus. The serial-type image forming apparatus performs the image forming operation by moving the recording head in a main scan direction while ejecting ink droplets onto a sheet of a recording medium. By contrast, the line-type image forming apparatus uses a line-type recording head that performs the image forming operation by ejecting the ink droplets without moving the recording head, that is, by keeping the recording head stationary while moving the sheet of the recording medium.
In such a serial-type image forming apparatus, a carriage on which the recording head is mounted moves reciprocally back and forth, inducing vibration in the image forming apparatus. In particular, in order to increase printing speed, the speed of movement of the carriage is increased, causing rapid acceleration and deceleration of the carriage when the carriage moves in the main scan direction. As a result, significant vibration occurs in the image forming apparatus when the speed of the carriage is rapidly increased or decreased. In a case in which the multi-functional image forming apparatus equipped with an image reading device such as a scanner, such vibration adversely affects scanning by the scanner, thereby causing degradation of a read image.
To counteract such a difficulty, various techniques have been proposed to reduce vibration of the carriage. For example, a damping member, also known as a counter weight, having substantially the same weight as that of the carriage, is attached to a timing belt that drives the carriage. The damping member is moved in the opposite direction of the carriage, thereby suppressing vibration of the carriage.
In another example of a vibration suppressing technique, a set of drive mechanisms, different from a drive mechanism that drives a printing head, is provided to move the damping member having the same weight as the printing head in a direction opposite the printing head at a constant speed.
However, although effective, there is a drawback to the above-described approaches. That is, because the damping member is attached to the timing belt that moves the carriage and always moves as the carriage moves so as to suppress vibration, fluctuation in any of the speed of the carriage, a moving load of the carriage, and the weight of the carriage as the ink is consumed from an ink tank on the carriage causes the damping member to vibrate undesirably. In particular, the damping member vibrates more than enough to suppress the vibration of the carriage. As a result, ink droplets are prevented from being accurately ejected onto a target position, thereby degrading imaging quality.
Furthermore, there is a drawback in this configuration in that the load against a drive source for moving the carriage increases. Since the damping member having the same mass as that of the carriage is used, the weight of the image forming apparatus as a whole increases, thereby complicating efforts to make the image forming apparatus compact.